RLSA needsLayout on customscrollbar thickness change.

Source/core/rendering/RenderLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 69 matching lines @@
 
 RenderLayerScrollableArea::RenderLayerScrollableArea(RenderLayer& layer)
     : m_layer(layer)
     , m_inResizeMode(false)
     , m_scrollsOverflow(false)
     , m_scrollDimensionsDirty(true)
     , m_inOverflowRelayout(false)
     , m_nextTopmostScrollChild(0)
     , m_topmostScrollChild(0)
     , m_needsCompositedScrolling(false)
+    , m_horizontalScrollbarChanged(false)
+    , m_verticalScrollbarChanged(false)
     , m_scrollCorner(nullptr)
     , m_resizer(nullptr)
 {
     ScrollableArea::setConstrainsScrollingToContentEdge(false);
 
     Node* node = box().node();
     if (node && node->isElementNode()) {
         // We save and restore only the scrollOffset as the other scroll values are recalculated.
         Element* element = toElement(node);
         m_scrollOffset = element->savedLayerScrollOffset();
@@ skipping 646 matching lines @@
         ASSERT(hasHorizontalScrollbar());
         m_hBar->setEnabled(true);
     }
 
     if (needsVerticalScrollbar && oldStyle && oldStyle->overflowY() == OSCROLL && overflowY != OSCROLL) {
         ASSERT(hasVerticalScrollbar());
         m_vBar->setEnabled(true);
     }
 
     // FIXME: Need to detect a swap from custom to native scrollbars (and vice versa).
-    if (m_hBar)
+    if (m_hBar) {
+        IntRect oldHrect = m_hBar->frameRect();
         m_hBar->styleChanged();
-    if (m_vBar)
+        if ((oldHrect != m_hBar->frameRect()) && m_hBar->isCustomScrollbar())
+            m_horizontalScrollbarChanged = true;
+    }
+    if (m_vBar) {
+        IntRect oldVrect = m_vBar->frameRect();
         m_vBar->styleChanged();
+        if ((oldVrect != m_vBar->frameRect()) && m_vBar->isCustomScrollbar())
+            m_verticalScrollbarChanged = true;
+    }
 
     updateScrollCornerStyle();
     updateResizerAreaSet();
     updateResizerStyle();
 }
 
+bool RenderLayerScrollableArea::didCustomScrollbarRectChanged()
+{
+    bool scrollbarRectChanged = false;
+    if (m_verticalScrollbarChanged || m_horizontalScrollbarChanged) {
+        scrollbarRectChanged = true;
+        m_verticalScrollbarChanged = false;
+        m_horizontalScrollbarChanged = false;
+    }
+    return scrollbarRectChanged;
+}
+
 bool RenderLayerScrollableArea::updateAfterCompositingChange()
 {
     layer()->updateScrollingStateAfterCompositingChange();
     const bool layersChanged = m_topmostScrollChild != m_nextTopmostScrollChild;
     m_topmostScrollChild = m_nextTopmostScrollChild;
     m_nextTopmostScrollChild = nullptr;
     return layersChanged;
 }
 
 void RenderLayerScrollableArea::updateAfterOverflowRecalc()
@@ skipping 712 matching lines @@
 void RenderLayerScrollableArea::setTopmostScrollChild(RenderLayer* scrollChild)
 {
     // We only want to track the topmost scroll child for scrollable areas with
     // overlay scrollbars.
     if (!hasOverlayScrollbars())
         return;
     m_nextTopmostScrollChild = scrollChild;
 }
 
 } // namespace blink